Device for stretching saw blades, particularly in sawmills



A. WASSERKAMPF 2,113,909

DEVICE FOR STRETCHING SAW BLADES, PARTICULARLY IN SAWMILLS April 12, 1938.

Filed June so, 1956 Ziy lg Patented Apr. 12, 1938.

DEVICE FOR STRETCHING SAW BLADES,

PARTICULARLY IN SAWIVIILLS Alfons Wasserkampf, Hanover, Germany, assignor to Otto Lauenstein, Wernigerode/Harz, Gere many Application June so, 1936, Serial No. 88,191

In Germany October 20, 1934 r 6 C a m.- This invention relates to a device for stretching saw blades, particularly in timber sawmills and automatic readjustment and compensation for any differences in length.

The invention is explained below with reference to theaccompanying drawing, in which:

Fig. 1 is a side-view of the tension device;

Fig. 2 is a section through the tension device along the line A--B in Fig. 1;

Fig. 3 is a plan-view of the tension device.

The tension device is mounted on the top bars a and b of the frame holding the blade s. In the example the tension device consists of a frame with a steel body I and a bar 2 fitted with feet 2a. Thebody I has two rows of mutually staggered cylindrical borings 3, all of which lead into a connecting channel 4. In each of the cylindrical borings 3 is inserted a piston 5, the stroke of which is, for example, restricted by stops.

The channel 4 is' in its turn connected, by means of a connection pipe 8, to the cylinder 6 of a filling or forcingpress 1. By means of the piston 9 fitted in the cylinder 6 the press liquid can be forced into the various borings 3, and thus any desired pressure can be exerted on the r pistons 5. The piston 9 can be moved forward by hand, for example by means of a wrench placed on the end of the piston-rod ID. The piston-rod is provided with a thread, and guided in a closure cap II with an internal screw thread, so that by turning the piston-rod II) the piston 9 can be displaced.

In order to allow for any differences in length in the saw blades s, a compensating cylinder !6 is connected by means of connection pipe l2 to the filling or forcing press 1. The piston l5 mounted in the cylinder I6 is pressed by a powerful compression spring 20, which constrains the piston IE to enter the cylinder l6, thus compensating any variations in pressure. The piston-rod M is led through the cylinder cover l3 and further to the outside. The projecting end is provided with a scale l8, from which it is possible to read the pressure of the liquid.

The tension device works in the following manner:

First, after removing the closure screw I9, a suitable press liquid is introduced, in such away that no air pocket is left. Thereupon all, the pistons-5 are lifted with slight pressure as far as' they will come out of their cylinders, by turning the piston-rod It], so. that all the piston heads lie in the same plane, which is advantageously somewhat higher than the top edge of the bar 2.

The saw blades are then suspended in known manner by means of wedge pins P, and the wedges are driven in by hand until'the heads of the pistons 5, depressed thereby, lie at about the same height as the top edge of the bar 2 and all the saw blades are stretched to practically the same initial tension. By advancing the piston 9 further into its cylinder the spring 20 is compressed until the pressure fluid actuating the pistons 5 reaches the pressure corresponding to the normal tension of the saw blades. This pressure can be read from the scale Hi.

If the saw blades should extend differently in length, for example in consequence of different degrees of heating, or if any press liquid should escape as the consequence of a lack of tightness, the resulting drop in pressure is made up by the compensating press, the piston l5, under the action of the powerful spring 20, being then pushed further into its cylinder l6. Larger drops in pressure can be made up for by readjustment of the piston-rod ID, that is to say, by means of the filling press 1.

I claim:

. 1. A device for uniformly stretching a plurality of saw blades comprising a movable frame, a plurality of saw blades arranged in said frame, members applied to said frame and movable independently of each other and each engageable with an end of one of said saw blades, and means to apply fluid pressure to said members to actuate the latter and exert a uniform stretching effect on the several saw blades.

2. A device for uniformly stretching a plurality of saw blades comprising holding means for the respective ends of a plurality of saw blades, connecting means connecting the holding means, members each applied to one of the holding means and engageable with an end of one saw blade, and means to apply fluid pressure to said members to actuate the latter and exert a uniform stretching effect on the several saw blades.

3. A device for uniformly stretching a plurality of saw blades, comprising a movable frame, a plurality of saw blades arranged in said frame, members movable independently of each other and each engageable with a saw blade, pressure liquid supply means, and means for applying pressure of the liquid to said members to actuate the latter and exert a uniform stretching effeet on the several saw blades, said members and both means being applied to said frame.

4. A device for uniformly stretching a plurality of saw blades comprising a frame, a plurality of saw blades arranged in said frame, members movable independently of each other and each engageable with one of said saw blades, means for applying liquid pressure to said members to actuate the latter and exert a uniform stretching effect on the several saw blades, and means for compensating for variations in the pressure of the actuating liquid, said members and both means being applied to said frame.

5. A device for uniformly stretching a plurality of saw blades comprising a frame having cross bars, a plurality of saw blades arranged in said frame, a body applied to one of said cross bars of said frame and including a plurality of bores, pistons movable in said bores and each engaging and tensioning one saw blade, a passage common to the several bores, and a pressure cylinder communicating with said passage and adapted to supply liquid under pressure to said bores to actuate said pistons. r

6. A device for uniformly stretching a plurality of saw blades comprising a frame having cross bars, a plurality of saw blades arranged in said frame, a body applied to one of the cross bars of said frame and including a plurality of bores, pistons movable in said bores and each engaging and tensioning one saw blade, a passage common to the several bores, a pressure cylinder communicating with said passage, a piston in the pressure cylinder and having screw threaded engagement therewith for varying the pressure of the fluid in said passage and bores, a compensating cylinder communicating with the pressure cylinder, a piston in the compensating cylinder, a compensating spring coasting with the piston in the compensating cylinder and normally tending to compress the liquid in said cylinder, and a rod on the piston of the compensating cylinder having a scale for indicating the pressure of the pressure liquid.

ALFONS WASSERKAMPF. 

